This invention relates to an image reading device having the reading function of a moving document exposure type (sheet-through reading) to read an image of an original document which is moving on the surface of a glass plate for slit exposure and the reading function of a moving optical system exposure type (flat-bed type) to read an image of an original document placed on a document base glass plate by moving an exposure unit under the document base glass plate, an image forming apparatus equipped with said image reading device such as an electrophotographic copying machine, a printer, a facsimile machine, and an image forming apparatus having a multiplex function.
With respect to a conventional image reading device having both of the reading function of a moving original exposure type and the reading function of a moving optical system exposure type, one that is noted in the publication of the unexamined patent application H3-23137 can be cited.
This image reading device is capable of image reading of two types, that is, a moving original exposure type in which an original document sheet is separated from a bundle of document sheets to be conveyed onto the surface of a glass plate for slit exposure by an automatic document feeder of a sheet-through reading type, which is attached to the upper side of the image reading device, and the document sheet moving on said glass plate for slit exposure is read by an optical system standing still under said glass plate for slit exposure, and a moving optical system exposure type in which an original document sheet is placed on a document base glass plate with the automatic document feeder opened, and the document sheet is read by moving an exposure unit.
In an image forming apparatus such as a copying machine equipped with an automatic document feeder of the above-mentioned sheet-through reading type, if an alien substance adheres to a position in the neighborhood of the optical axis on the rear surface of the glass plate for slit exposure, a white streak image or a black streak image is produced on a recording paper sheet on which an image is formed.
Because it is difficult to let a user practice the cleaning of the glass plate for slit exposure by removing smudges on the rear surface of it, a service for maintenance should be requested to a trader concerned having a specialized technique (serviceman call).
It is an object of this invention, in order to solve the above-mentioned problem, to provide an image reading device and an image forming apparatus provided with a cleaning means having an extended durability of a cleaning member to the utmost extent and preventing the re-adhering of an alien substance after cleaning, by cleaning only the portion near the optical axis on the rear surface of the glass plate for slit exposure.
(1) An image reading device of this invention to accomplish the above-mentioned object is an image reading device having the reading function of a moving original exposure type to read an original document which is moving on the surface of a glass plate for slit exposure by an exposure unit standing still at a specified position under said glass plate for slit exposure, and the reading function of a moving optical system exposure type to read an image of an original document placed on a document base glass plate by moving an exposure unit under said document base glass plate, wherein cleaning means for cleaning the rear side of said glass plate for slit exposure is provided.
(2) An image forming apparatus of this invention to accomplish the above-mentioned object is equipped with an image reading device as set forth in the above-mentioned paragraph (1), and image forming means for forming an electrostatic latent image on an image carrying member by image exposure means on the basis of an image signal of an original document obtained by said image reading device, and visualizing said electrostatic latent image.